Adds more possible challenges to The End dragon battle:
-sculk sensors in The End, and that means wardens
-shulker-defense towers
-phantom & dragon
-end-crystals that defend themselves with death-rays, battle cages, and moats
-extra-tall towers
-crater-egg-laying dragon
-hollow towers
-elder dragon
-magic dragon (can cast blindness, slowness, weakness, mining fatigue, summon an ender-vex, and more)
-multiplying baby endermen (so long as one lives, more will come, so eliminate them all)
-giant & dragon
-twin dragons
-wither & dragon
-water-flooded End
-lava-flooded End

Different modes to chose The End battle enhancement:
-sequential: each time you spawn the dragon it will advance to the next challenge
-moon-phase: the challenge you get will depend on the moon's phase
-random: the challenge you get will be like a box of chocolates*

* you never know what you're going to get

Once you defeat a challenge, and re-spawn the dragon, The End will repair itself, so the next battle can be just as fun as the last.